From the viewpoint of biology, head hair and body hair are tissues that protect important organs and body parts, such as the head, chest, and limbs. However, in recent years, there has been an increasing tendency that little body hair on particular body parts (e.g., limbs) is considered favorable from the viewpoint of aesthetic appearance.
Examples of a body hair removal method include a mechanical removal method using a shaver, a hair remover, or the like, and a chemical removal method using an epilation or depilation agent. However, such body hair removal methods may involve physical or chemical stimulation of the skin, and further, are not yet satisfactory in terms of hair growth suppressing effect. Thus, the aforementioned methods require a retreatment for body hair removal after the elapse of a certain period of time. Thus, demand has arisen for reducing the frequency of body hair removal treatments.
Conventionally, in the selection or evaluation of a hair growth agent or a hair growth suppression agent, a candidate substance was applied to the skin of a living body (Patent Documents 1 to 3) or administered to the organ culture of hair follicles of human, mouse, rat, or pig in vitro, subsequently the degree of the extension of hair or the growth of the hair follicle was measured, and the hair-growing or hair-suppressing action of the candidate substance was evaluated based on the results of the measurement (Patent Documents 4 to 7, Non Patent Documents 1 to 3). Considering the efficiency and the accuracy of the evaluation, an in vitro assay is more preferable. However, there are problems with in vitro organ culture of hair follicles that acquisition of the hair follicle to be used as a sample may be difficult, culture takes time and labor, and evaluation is time-consuming as it takes several days until the extension of hair or the growth of the hair follicle is observed, and so on. The development of an in vitro screening system for more efficient selection or evaluation of a hair growth agent or a hair growth suppression agent is demanded.
Patent Document 7 describes that such heat shock proteins as HSP-27, HSP-70, and HSP-90 are present in the human hair follicle, that administration of an anti-HSP-27 antibody to the hair follicle led to an observation of a significant reduction in the development of hair fiber, and that the growth of the human hair follicle was reduced by administration of geldanamycin, which is an HSP-90-specific inhibitor, or KNK437, which is an HSP synthesis-inhibitor, in a dose-dependent manner. However, given that there are so many kinds of heat shock proteins and their functions are also diverse, the molecular mechanisms involved in hair growth of the aforementioned heat shock proteins remain unknown, and further, it has been impossible to predict whether other heat shock proteins could be involved in hair growth.
Funabarasou (Cynanchum atratum) is a perennial plant belonging to the genus Cynanchum in the family Asclepiadaceae, and its root is used in a Kampo prescription such as byakubito. Funabarasou (Cynanchum atratum) is known to have a medicinal effect such as alleviation of fever and cooling of blood, antipyresis, and a diuretic effect. Further, cynanchol, which has the action of cardiac glycosides, is known as its medicinal ingredient.
Patent Document 8 discloses a skin external preparation for hair growth containing an extract of a crude drug, including byakubi, having an activating action of body fluids (shineki-sayou) and the active ingredient of the extract as well as an extract of a crude drug having an angiogenesis activation action and the active ingredient of the extract. Patent Document 9 describes the use of a composition containing the extract of a plant belonging to the family Asclepiadaceae for the cosmetic treatment of human skin including inhibition, suppression, or retardation of the growth of the body hair. However, it has not been revealed how funabarasou (Cynanchum atratum) affects hair growth by itself.